An end effector includes a first jaw member, a second jaw member, a drive beam, and a drive screw. The second jaw member is pivotally movable relative to the first jaw member between an open position and a closed position. The drive beam is positioned to engage the second jaw member and is longitudinally movable through the first and second jaw members. The drive screw is supported within the first jaw member and includes a threaded portion coupled to the drive beam such that rotation of the drive screw imparts longitudinal movement of the drive beam along the second jaw member to move the first and second jaw members from the open position to the closed position.
